The purpose of this application is to obtain a Laser Scanning Cytometer (LSC) as a Shared Instrument Facility for quantitative cytometry of normal and pathological specimens. The equipment is intended to support researchers at UCLA and surrounding academic institutions, and to aid in project development within the Jonsson Comprehensive Cancer Center and the UCLA School of Medicine. The instrument will be managed by the UCLA LSC Users Group, comprised of researchers with established expertise and interests in cytometry. No instrument of this type are currently available at UCLA. The LSC is the first commercial instrument to allow efficient quantitative cytometry of attached cells, tissue sections, and other slide-based materials. As such, it represents a major advance for the analysis of adherent cell populations. Similar to flow-cytometers, the LSC provides quantitative laser activated fluorescence cytometry. However, there are numerous advantages to the LSC that make investment in this instrumentation essential to support advanced studies in cell and tumor biology. No other instrument provides quantitative histogram analysis of subcellular events while maintaining tissue and subcellular architecture. The technology also provides "gating" functions to permit re-acquisition of individual cells for more extensive imaging or molecular characterization. Within this framework, there are expanded opportunities to detect rare events, and to distinguish subcellular particles that are poorly resolved in flow-based measurements. In addition to rapid quantitation of microscopic samples, the methodology permits cost savings to traditional addition to rapid quantitation of microscopic samples, the methodology permits cost savings to traditional cytometry users by reducing sample sizes and antibody usage. This LSC instrument is specifically requested as a shared instrument, to support the following studies within the Johnson Comprehensive Cancer Center and the UCLA School of Medicine: i) analysis of transcriptional regulators in breast and ovarian cancer cells; ii) quantification of subcellular particles in tumor cells; iii) quantitative analysis of neuronal differentiation markers during PC12 differentiation; iv) quantitation of endothelial cell shape changes during response to angiogenic mediators; v) analysis of tumor/stromal cell complexes and immune mediators in ovarian cancer cells; vi) analysis of NO induced apoptosis in tumor cells; vii) immuno-phenotyping of tumor biopsies; viii) cellular interactions between thynocytes and AIDS infected cells. In addition, the members of the UCLA LSC Usere Group propose to act as an informational and technical resource to aid development of LSC related projects within the UCLA research community.